Frac sand is a pure quartz sand with durable round grains and is a crush-resistant material used by the petroleum industry. It is used in a hydraulic fracturing process, known as “fracking”, to produce petroleum fluids including natural gas, oil from rock formations which lack adequate pore space for these petroleum fluids to flow to a well. The hydraulic fracturing process generates fractures in the rock by drilling a well into the rock, sealing the well in the petroleum-bearing zone of the well and pumping liquid into the petroleum-bearing zone of the well. The liquid is treated with chemicals and has frac sand mixed therein. Large pumps above ground increase the pressure in the sealed portion of the well until the pressure exceeds the breaking point of the rocks. When the rocks fracture, the liquid containing frac sand and enters the fractures. The pressure is then relieved by turning the pumps off. The frac sand inside the rock fractures must be great enough to keep the fractures open. Because the frac sand props the fractures open, it is known as a “proppant” in the industry. Frac sand is a highly pure silica sand ranging in diameter from 0.1 millimeter to over two millimeters.
The demand for frac sand has increased in the past few years because more and more oil and natural gas wells use fracking. A hydraulic fracturing job on one well can require a few thousand tons of sand.
Frac sand requires processing after being mined to optimize its performance. At a processing plant, the frac sand is washed to remove fine particles. After washing, the sand is stacked in piles to allow the water to drain through the pile faster. However, such drainage takes time and often does not dry the frac sand adequately. After being partially dried, the sand is placed in a rotary drier. Operating a rotary dryer requires a great deal of energy because the frac sand entering the rotary dryer is wetter than desired. Its moisture content would preferably be lower entering the rotary dryer, thereby reducing the time required for the frac sand to be inside the rotary dryer to achieve the desired moisture content.
Therefore, there is a need for a drainage system for drying frac sand in less time than known drainage systems.
There is further a need for a drainage system for drying frac sand which uses gravity and costs less than known systems.
There is further a need for a method of drying frac sand which uses less energy than known drying methods.